The sewer collection system is among the most valued assets of a community's infrastructure. As these systems age, problems associated with infiltration and structural deterioration significantly increase. With much of America's underground infrastructure well beyond fifty years in age, improved methods of rehabilitating and sealing sewer collections systems will be critical for this vital network. Current problems of system overload and bypass are largely attributed to the deteriorating conditions of the miles of collection and transmission pipelines. The most common method of rehabilitating and reconstructing sewer systems has been simply to replace aging sewer lines and replace the manholes. This method required digging out the sewer lines, which is a time consuming and expensive procedure. In populated areas, this procedure also results in substantial disruption of traffic and personal inconvenience. More recently, attention has begun to shift to reconstructing the sewer system. Two primary factors that created this shift were the introduction and acceptance of trenchless technology for pipeline reconstruction and the development and refinement of pipe inspection systems. Trenchless technology has provided a feasible and politically sound alternative for addressing problems in the sewer system. The most common trenchless technology includes lining the sewer lines with a cured in place pipe (CIPP) having a thermoset resin which is bonded to the sewer line and an interior impermeable preferably reduced friction film, such as polyurethane, on the interior surface. Improvements in lining manholes with a polyurea or polyurethane lining have also been introduced. These improved systems have not, however, been integrated in a way which prevents infiltration and inflow of groundwater into the manholes particularly along the exterior of the cured in place pipe.
The trenchless cured in place pipe technology generally includes inserting and inflatable tubular liner into the sewer line from one end. The liner includes an outer layer of felt of synthetic fibers, such as polyester, nylon or acrylic fibers, saturated with a thermoset resin and an inner layer bonded to the fibrous layer, such as a film of polyurethane, polyethylene, polyvinyl chloride, Neoprene, polyester or the like. In one method developed by Insituform International N.V. of the Netherlands, the tubular liner of the cured in place pipe is formed with the impermeable film on the exterior surface and the felt on the interior surface. When the flexible lining tube is inserted in the pipeline or passageway, one end is anchored and then the remainder of the tube is everted through the anchored ends so that the tube everts into the pipeline or passageway and onto the surface to be lined. The everting medium is usually liquid and when the inversion process is completed, the liquid remains inside the inverted tube to keep the pipeline or passageway surface shape while the resin in the felt layer cures. The resin may include a catalyst and may be cured by any conventional means, including heated water, air or even radiant heating. Examples of this technology are disclosed in U.S. Pat. Nos. 4,009,063, 4,439,469 and 4,581,247. Upon curing, the resin impregnated felt liner becomes rigid and is permanently bonded to the interior surface of the sewer line and the interior impermeable film reduces friction.
Improved methods of lining or relining manholes has also been more recently introduced. The preferred method includes spraying the internal surfaces of the manhole with a fast curing elastomeric material, preferably polyurea, whereby a homogeneous, non-porous and monolithic coating or lining is formed on the interior surfaces of the manhole. The surfaces of the manhole to be lined or relined will generally require preparation by cleaning the brick, tile, concrete block or mortar or foreign material, as required. In the most preferred method of lining or relining a manhole, a primer such as an aqueous solution of silane is sprayed on the prepared surface to improve adhesion of the elastomeric material to the interior surfaces of the manhole. Although the manhole lining is preferably a polyurea elastomeric material prepared by rapidly mixing and initiating the reaction of an isocyanate-terminated compound with an amine-terminated compound, it is also possible to line manholes using a polyurethane coating if the manhole is thoroughly dried before coating. U.S. Pat. Nos. 5,405,218 and 5,415,499 of Foamseal of Oxford, Mich. disclose an improved method of lining or relining manholes using a polyurea coating or lining.
As set forth above, however, the problem of infiltration and inflow of groundwater entering the sewer system remains even with the improved technology described above. Where a cured in place pipe is used in the sewer lines, groundwater will continue to flow along the exterior surface of the sewer lines into the manholes. Hydraulic capacity is thereby reduced due to excess flow which can impede future growth and development and when the sewer system becomes hydraulically overloaded, diluted untreated sewage may be bypassed directly into surface water. Thus, there remains a need to develop a method of integrating the lining of sewer lines and manholes to form a sealed system which prevents infiltration and inflow of groundwater around the cured in place pipe and the original sewer line into the manholes.